1. Field of the Invention
The present invention relates to an image recording method and apparatus for preventing forgery of specific original images including bank notes.
2. Description of the Related Art
With recent development of technology in the field of color photocopy machines and color scanners, there is some fear of forgery of bank notes and bills using this technology. Accordingly, color photocopy machines that prevent forgery have been proposed. The color photocopy machine with the forgery-preventing function reads an image of an original by irradiating the original with an illuminating light, compares the original image with previously stored specific images representing bank notes to determine whether the original is a bank note, and interferes with photocopying of the original image on an affirmative determination.
FIG. 1 shows the timing of each step in an image recording process with a standard color photocopy machine. After a pre-scanning step P1 (from the start through a first time point t1) for obtaining information regarding an original, a first scanning step P2 is executed simultaneously with a first latent image forming step P3 (the first time point t1 through a second time point t2). A blue (B) light component of the original is obtained at the first scanning step P2, and a latent image is formed on a photosensitive drum with a light beam of the B component at the first latent image forming step P3. In the time period between the second time point t2 and a third time point t3, a second scanning step P4 for obtaining a green (G) light component of the original is executed simultaneously with a second latent image forming step P5 for forming a latent image on the photosensitive drum with a light beam of the G component and a first transfer step P6 for transferring the latent image formed with the light beam of the B component onto a sheet of paper. The respective components of the light beam are successively transferred onto the sheet of paper with a certain delay from the scanning step and the latent image forming step for the corresponding components.
The color photocopy machine having the forgery-preventing function determines whether the original is a bank note at the pre-scanning step P1 and interferes with the subsequent steps based on an affirmative determination.
The identification of the original may be performed at any scanning step P2 or P4 instead of the pre-scanning step P1. In any case, immediately after recognizing the original as a bank note, the color photocopy machine totally interferes with the subsequent steps for preventing duplication of the original. This means that even part of a bank note like one half or one third is not duplicated at all.
This preventing process is, however, available only in color photocopy machines and is not applicable to color scanners because of the following reasons. In a color scanner, as shown in FIG. 2, a scanning process P11 for reading an image of an original is executed simultaneously with image recording steps P12, P13, P14, and P15 for recording color separation images of Y (yellow), M (magenta), C (cyan), and, K (black) separations. When the original is recognized as a bank note in the middle of the scanning step P11, the respective image recording steps P12, P13, P14, and P15 have already been implemented to some extent. Part of a bank note, like one half or one third, has thus been reproduced in a complete form on a recording film. Repetition of such process gives a plurality of partial images of the bank note. A complete bank note can be reproduced by patching the plurality of partial images. Although some color scanners recently proposed have a pre-scanning function for smooth set-up, the pre-scanning process is not essential in color scanners.